Generally, ferrocenoyl derivatives are very useful as the intermediate material for producing highly active functional materials having a ferrocene skeleton, such as functional polymers, LB films, surfactants, charge-transfer complexes, ion sensors, masking reagents, and coupling agents.
Such ferrocenoyl derivatives have heretofore been produced according to a process in which a carboxylic acid is converted into acid halide and then the resulting acid halide is reacted with a ferrocene derivative in the presence of a Lewis acid catalyst such as aluminum chloride.
That process, however, will involve byproducts in which each of two five-membered rings of ferrocene derivatives has been acylated. Accordingly, to inhibit such byproducts, the way of adding ferrocene derivatives must be selected. Moreover, when a compound containing halogen atom is used as the carboxylic acid, the reaction temperature should be controlled to be under 5.degree. C., so as to inhibit dehalogenation reaction.
Further, the acylation reaction of ferrocene derivative with the use of catalysts such as polyphosphoric acid has been known (J. Am. Chem. Soc. 79,3290 (1957)). It is, however, an intramolecular reaction, and any intermolecular acylation of ferrocene derivatives which is required for selectivity has not been known.
Particularly, to produce a ferrocenoyl derivative having carboxyl group, a very complicated process has been required wherein one carboxylic acid of dicarboxylic acid is esterified by use of disproportionation reaction, then the other unreacted carboxylic acid is acid-halogenated, and the resulting product is reacted with ferrocene derivative under the condition of usual Friedel-Crafts reaction, to obtain ferrocenoyl derivative carboxylate, and after that, said ester is hydrolyzed (PCT Int. Appln. Laid-Open WO89/01939).
Above process, however, required so many steps and complicated operations but the yield was insufficient that it was not suitable for practical use.